The invention relates to a sealed flexible sachet, containing at least one powder substance for the preparation of a beverage including substances compacted into a cake by extraction under pressure and to manufacture of the sachet.
The use of pre-metered and pre-packaged portions of ground coffee for the preparation of expresso-type coffee has the advantage that it facilitates the coffee preparation operations while ensuring that the quality of the product is relatively consistent.
These portions are currently provided in three main forms. According to a first version, pre-packaged portions disclosed in Swiss Pat. No. 636 311, and in U.S. Pat. No. 5,012,629 and in European Patent Application Publication No. 272 432 are formed by two sheets of filter paper sealed over their periphery and filled with ground coffee. This solution has the drawback that an oxygen-barrier outer packaging is required to prevent oxidation of the product during storage, entailing additional costs and a supplementary operation for the consumer who has to remove it before the desired coffee can be extracted.
According to a second version, disclosed in PCT Patent Application Publication No. WO 92/07775, the portion is formed by a sealed capsule opening into its extraction device under the action of the introduction of the extraction fluid, after deformation and then perforation by pointed members.
This capsule, formed by a sealed envelope forming a lateral wall and two walls, one of which forms the base of the cartridge and the other of which closes the opposite end of the cartridge, has the drawback that it makes use of different packaging materials, some of which have to be thick enough to make them semi-rigid, and can be used only in one direction, i.e., with the cap surface upwards in an extraction device which is completely adapted to the capsule and to its arrangement.
According to a third version, U.S. Pat. No. 3,607,297 discloses sachets for the preparation of a beverage in the form of a strip having filling cavities and a flat cap on the upper surface. According to this patent these sachets are adapted for gravity flow and have to be perforated on both surfaces by toothed plates, one of which is pushed by a spring.